1. Field of the Invention
This invention relates in general to braking systems and, more particularly, to an interlock system for incorporation as original equipment. This interlock system includes a simple brake control device that provides a braking function when the system is engaged and a failure is detected, is easily installed in the foot valve to simplify installation, and improves failure mode protection.
2. Discussion of the Art
It is known in the industry, for example, as shown and described in U.S. Pat. No. 4,838,617, to interlock brakes with operation of the door. When the door is opened, the brakes are applied and cannot be released while the door remains opened. As taught in U.S. Pat. No. 4,838,617, a solenoid is energized and shifts a plunger to a blocking position in response to a door being opened. A valve maintains pressure in the brake line and prevents release of the brakes even if actuating pressure on the brake pedal is released. Once the door is closed, the solenoid is deenergized and the brakes are released.
Other systems, for example as taught in U.S. Pat. No. 4,200,167, provide an interlock between the door handle of a bus and a series of switches, such as a brake light switch, gear shift, and a driver control switch before the door is permitted to open.
Presently, some state laws require that an operator park a bus during passenger pickup. This necessitates that the operator or driver actuates a park brake, for example, pulling an actuating lever to apply a park brake. Repetitively actuating and deactuating the park brake can cause extreme fatigue to the driver and premature wear of components in the brake system.
The present applicant suggests that a safe course of action can be achieved by urging the driver to stay seated with his foot on the brake pedal during a door open state. In other words, it is not necessary to actuate the park brakes. Instead, it would be desirable to have a system that provides a service brake application as long as the driver remains seated with his foot depressing the foot pedal to effect a normal service brake application.
It is deemed desirable to have the driver cause a service brake application to both the drive and steer axles and be in a position to undertake further action if necessary. It is further desirable to provide a system that monitors certain activities of the driver, e.g., whether the driver is seated or wearing his seat belt. If not, it would be desirable to apply the brakes automatically if the driver exits the seat with the interlock feature actuated. In addition, an alarm or signal is provided if certain requirements are not met.
The present invention contemplates a new and improved apparatus and method that overcomes the above-referenced problems and others and provides a simple, effective solution which can be integrally incorporated into OEM systems.
More particularly, a simple auxiliary brake control device or interlock assembly is provided so that the service brakes are automatically applied under selected conditions. An alarm associated with a door/service interlock assembly is responsive to application of the brakes under certain circumstances.
The system is activated and deactivated in response to the operator turning on the flashing caution lights and opening the bus door.
A pressure indicator monitors air pressure in an auxiliary line provided between a source of air pressure and a foot valve.
A low-pressure indicator is actuated in response to a no or low-pressure application of the air and activates the applied foot valve feature causing an alarm to alert the operator.
A principal advantage of the invention is realized by urging the driver to stay seated when the auxiliary brake control system is activated (e.g., when caution lights have been turned on and the door opened) so that a normal service brake application is used.
Still another advantage of the invention is the ability to provide increased confidence that results by causing the parking brakes to be automatically set should the operator exit the seat with the system engaged.
Yet another advantage is the reward provided to the driver in disabling the system, including the alarm, if the park brake is applied.
Still other advantages and benefits of the invention will become apparent to those skilled in the art upon a reading and understanding of the following detailed description.